All categories

3 years ago

What are the coordinates of the vertex for f(x) = x2 + 4x + 10?

1 answer:

3 0

F(x) = x² + 4x + 10

f(x) - 10 = x² + 4x

perfect square:
x² + 4x + 4 ⇒ (x + 2)²

(x + 2)² = x(x+2) + 2(x+2) = x² + 2x + 2x + 4 = x² + 4x + 4

f(x) - 10 + 4 = x² + 4x + 4
f(x) - 6 = (x+2)²
f(x) = (x+2)² + 6

You might be interested in

A building has n floors numbered 1,2,...,n, plus a ground floor g. at the ground floor, m people get on the elevator together, a

fomenos

Let $X_i$ be the random variable indicating whether the elevator does not stop at floor $i$ , with

$X_i=\begin{cases}1&\text{if the elevator does not stop at floor }i\\0&\text{otherwise}\end{cases}$

Let $Y$ be the random variable representing the number of floors at which the elevator does not stop. Then

$Y=X_1+X_2+\cdots+X_{n-1}+X_n$

We want to find $\mathrm{Var}(Y)$ . By definition,

$\mathrm{Var}(Y)=\mathbb E[(Y-\mathbb E[Y])^2]=\mathbb E[Y^2]-\mathbb E[Y]^2$

As stated in the question, there is a $\dfrac1n$ probability that any one person will get off at floor $n$ (here, $n$ refers to any of the $n$ total floors, not just the top floor). Then the probability that a person will not get off at floor $n$ is $1-\dfrac1n$ . There are $m$ people in the elevator, so the probability that not a single one gets off at floor $n$ is $\left(1-\dfrac1n\right)^m$ .

So,

$\mathbb P(X_i=x)\begin{cases}\left(1-\dfrac1n\right)^m&\text{for }x=1\\\\1-\left(1-\dfrac1n\right)^m&\text{for }x=0\end{cases}$

which means

$\mathbb E[Y]=\mathbb E\left[\displaystyle\sum_{i=1}^nX_i\right]=\displaystyle\sum_{i=1}^n\mathbb E[X_i]=\sum_{i=1}^n\left(1\cdot\left(1-\dfrac1n\right)^m+0\cdot\left(1-\left(1-\dfrac1n\right)^m\right)$
$\implies\mathbb E[Y]=n\left(1-\dfrac1n\right)^m$

and

$\mathbb E[Y^2]=\mathbb E\left[\left(\displaystyle\sum_{i=1}^n{X_i}\right)^2\right]=\mathbb E\left[\displaystyle\sum_{i=1}^n{X_i}^2+2\sum_{1\le i$

Computing $\mathbb E[{X_i}^2]$ is trivial since it's the same as $\mathbb E[X_i]$ . (Do you see why?)

Next, we want to find the expected value of the following random variable, when $i\neq j$ :

$X_iX_j=\begin{cases}1&\text{if }X_i=1\text{ and }X_j=1\\0&\text{otherwise}\end{cases}$

If $X_iX_j=0$ , we don't care; when we compute $\mathbb E[X_iX_j]$ , the contributing terms will vanish. We only want to see what happens when both floors are not visited.

$\mathbb P(X_iX_j=1)=\left(1-\dfrac2n\right)^m$
$\implies\mathbb E[X_iX_j]=\left(1-\dfrac2n\right)^m$
$\implies2\displaystyle\sum_{1\le i$

where we multiply by $n(n-1)$ because that's how many ways there are of choosing indices $i,j$ for $X_iX_j$ such that $1\le i$ .

So,

$\mathrm{Var}[Y]=n\left(1-\dfrac1n\right)^m+2n(n-1)\left(1-\dfrac2n\right)^m-n^2\left(1-\dfrac1n\right)^{2m}$

4 0

3 years ago

Shane is a salesperson. He earns an hourly wage of $8.00 per hour, plus he receives a commission of 7% on sales he makes. Write

Arisa [49]

Answer:

8X+.07Y=W

Step-by-step explanation:

x is your hours and y is your sales

he makes 8 an hour, hence 8X or 8 x X

7 percent written as a decimal is .07 and his commission for sales, so .07Y

add them together and you get your equation:

8X+.07Y=W

7 0

3 years ago

Radius of a circle with a circumference of 50.26

klio [65]

Answer:

16 cm

Step-by-step explanation:

Circumference is equal to 2 pi r.

Isolating r gives us C/2pi = r

50.26/2pi = 8, exactly.

Diameter is equal to 2r, so the diameter is 16 cm.

7 0

3 years ago

Read 2 more answers

Valley schools have a student population of 1,608 students .if there are an equal number of students in the 6th grade levels, ho

alisha [4.7K]

Answer:

268

Step-by-step explanation:

1608/6= 268

hope this helps!

5 0

3 years ago

Which of the following is equal to 5^6/5^2?<br><br> 5x5x5<br> 5x5x5x5

lisov135 [29]

I hope this helps you

3 0

3 years ago

Read 2 more answers